What Is Atrial Fibrillation?

This type of irregular heartbeat affects millions of Americans. Understanding the causes and symptoms of atrial fibrillation can help you manage the condition and prevent additional complications.

Atrial fibrillation is a condition that affects millions of Americans. This type of irregular heart rhythm, also known as an arrhythmia, is the most common serious irregular heartbeat, especially in people over 60.

Your heart’s rhythm is normally controlled by a structure in the upper part of your heart called the sinoatrial node. This node sends an electrical signal to the rest of your heart that keeps your heart beating at about 60 to 100 beats a minute. This is known as your normal sinus rhythm.

In atrial fibrillation, the sinoatrial node does not direct the heartbeat. Rather, it causes heartbeats to start from many locations in upper chambers of the heart, or the atria. “These irregular heartbeats all over the atria cause the upper part of the heart to quiver like a bag of worms,” says Danya L. Dinwoodey, MD, a cardiologist at the Lahey Clinic in Burlington, Mass.

The term atrial fibrillation refers to the quivering, or fibrillation, of the upper parts of the heart. It can cause your heart to beat very quickly and inefficiently, which can be dangerous.

The cause of atrial fibrillation can vary from person to person, and sometimes it’s difficult to determine. In many cases, there is a combination of causes. “The most common causes are high blood pressure or an abnormal heart valve,” explains Dr. Dinwoodey.

Other causes of atrial fibrillation include:

Coronary artery disease (the clogging of the arteries of the heart that may cause a heart attack)

Heart failure

Heart defects you are born with

Pericarditis (an infection of the lining of the sac that surrounds the heart)

An overactive thyroid gland

Risk Factors for Atrial Fibrillation

The biggest risk factor for atrial fibrillation is age. The condition occurs more often in people over 60, and the risk for developing it increases as you get older.

Not everyone who has atrial fibrillation experiences symptoms. “Some people are very aware of their symptoms and can tell right away when an episode of atrial fibrillation starts and stops,” Dinwoodey says. “Other people may not notice any symptoms. For people who have symptoms, the most common ones are decreased tolerance for exercise and feeling a flutter in the chest.”

Other symptoms of atrial fibrillation may include:

Shortness of breath

Dizziness

Chest pain

Tiredness

There are two different types of atrial fibrillation, and the frequency of symptoms varies with each type. Paroxysmal atrial fibrillation begins suddenly and often stops on its own. Persistent atrial fibrillation lasts for more than a week, and while it may stop on its own, it frequently requires treatment. Both types may become permanent over time.